TBD

High Energy Seminar

Wednesday, November 1, 2017 - 12:30pm

Phillips Auditorium

The warm accretion disk around the Galactic Center Black Hole SgrA*

Speaker:

Elena Murchikova

Institution:

Caltech

Abstract

The Milky Way's supermassive black hole SgrA* is our most important
key to understanding black hole physics, their immediate environments
and growth. Yet the properties of its immediate environment are
largely unconstrained, and the accretion flow onto it is a mysterious
topic. The only things that we know with certainty are that the amount
of the material around the black hole is small and that the accretion
is very low. We will discuss a novel probe of the Galactic Center
black hole environment - submm recombination lines of hydrogen - and I
will report the first detection of the warm ionized disk within
~0.008pc radius around SgrA* with ALMA. We will estimate its
properties and discuss its possible origin. We will also talk about
the upcoming close flyby of the S2 star about the Galactic Center in
spring 2018 and what it can teach us about the region.

Emission from stars disrupted by supermassive black holes (SMBHs) is a powerful tool to address fundamental questions in astrophysics: What is the mass distribution for SMBHs? What is the SMBH occupation fraction in galaxies? Detailed observations of tidal disruption events (TDEs) are valuable tools to study the astrophysical processes powering the emission around SMBHs, revealing the otherwise quiescent population. In the last decade, optical time-domain surveys have allowed us to discover an increasingly diverse population of nuclear flares associated to TDEs. However, their spectroscopic signature in the UV has only been observed for three events so far, one of the being iPTF15af. In my talk, I will present optical and UV photometric and spectroscopic observations for this TDE, discovered by the intermediate Palomar Transient Factory (iPTF) survey. I will present its properties in the context of other similar events and discuss about a possible connection to N-rich QSO.